1. Field of the Invention
The present invention relates to an image reader in which an image sensor, which irradiates light on a recording-objective medium (reading-objective medium), photoelectrically converts reflected light from the recording-objective medium and outputs the reflected light to a control unit, is mounted on a carriage, and the carriage is reciprocated by a scanning mechanism in parallel to a surface for placing a recording-objective medium, and to a method of producing the image reader.
2. Description Of The Related Art
As disclosed in U.S. Pat. No. 6,903,849 (corresponding to Japanese Patent Application Laid-open No. 2001-346006) for example, a so-called flat bed scanner, in which an image sensor such as CCD (Charge Coupled Device) or CIS (Contact Image Sensor) provided inside a placing-reading table is mounted on a carriage for reading an image of an original by scanning, is known as an image reader mounted in a copying machine or a multifunction machine.
FIG. 13 is a diagram showing a conventional image sensor and a carriage. As shown in the diagram, an image sensor 90 has a rectangular parallelepiped shape with a longitudinal direction being primary scanning direction (main scanning direction). The image sensor 90 has an upper surface 91, which is a surface for reading an image or a letter. The image sensor 90 is a so-called CIS, in which light is irradiated from a light source provided inside the image sensor 90 to the outside via the upper surface 91, and reflected light from a medium to be read (recording-objective medium) incidents on the image sensor 90 via the upper surface 91. The incident reflected light is collected to a photoelectric conversion element by a lens, thereby outputting an electric signal corresponding to the intensity of the reflected light.
The carriage 92 is for holding the image sensor 90. As shown in the diagram, the carriage 92 is a container having an open upper side and capable of enclosing the image sensor 90. The image sensor 90 is accommodated in the carriage 92 to be enclosed therein, and is positioned in a primary scanning direction and a secondary scanning direction by engagement structures having projection and recess shapes for example, which are formed appropriately on the image sensor 90 and the carriage 92.
The carriage 92 is arranged to be reciprocapable along a guide shaft of a scanning mechanism by engaging with the guide shaft. Further, the carriage 92 is coupled to a timing belt of the scanning mechanism and reciprocates by receiving drive transmission via the timing belt. An engaging portion with the guide shaft and a coupling portion to the timing belt are formed on a bottom surface of the carriage 92. Further, to the image sensor 90, an electric cable for outputting an electrical signal and supplying power to the light source and so forth is connected. A connector portion to be connected to the electric cable is provided on a bottom surface of the image sensor 90. The electric cable connected to the connector portion is drawn inside a space between the image sensor 90 and the carriage 92 and extended from a predetermined position on the carriage 92 to the outside of the carriage 92.
The image sensor 90 performs reading of an image of a recording-objective medium with its longitudinal direction being the primary scanning direction and a direction orthogonal to the primary scanning direction being the secondary scanning direction. Therefore, the length in the longitudinal direction of the image sensor 90 corresponds to the width of a recording-objective medium of the maximum readable size, and inside the image sensor 90, a light source and a photoelectric conversion element which correspond to the width of the recording-objective medium of the maximum size are provided. Therefore, depending on whether the recording-objective medium of the maximum readable size is A4 size or A3 size for example, the length in the longitudinal direction of the image sensor 90 is different. As a matter of course, the image sensor 90 capable of reading a recording-objective medium of the A3 size can read an image of a recording-objective medium of the A4 size, but naturally, the costs thereof increase as the length of the image sensor 90 becomes long. Therefore, using the image sensor 90 corresponding to, for example, the A3 size for all image readers without considering the frequency of usage, users' needs and the like is not appropriate in view of the costs and the size of the apparatus. In short, it is preferable to produce image readers capable of reading up to the A3 size and image readers capable of reading up to the A4 size for example according to respective demands for them.
As the carriage 92 accommodating the image sensor 90, a carriage corresponding to the length of the image sensor 90 is designed. Specifically, dedicated carriages 92 according respectively to lengths of the image sensor 90 corresponding to the A3 size and the image sensor 90 corresponding to the A4 size have been used.
Further, to the connector portion provided on the bottom surface of the image sensor 90, the electric cable cannot be connected in a state that the image sensor 90 is accommodated in the carriage 92. Therefore, there is adopted a working method such that after the electric cable is drawn inside the carriage 92 in advance and immediately before the image sensor 90 is engaged with the carriage 92, the electric cable is connected to the connector portion. For example, the image sensor 90 and the carriage 92 are engaged pivotally by a shaft and a bearing, and in this engaging state, after the electric cable is connected to the connector portion, the image sensor 90 is pivoted about the carriage 92 so as to accommodate the image sensor 90 in the carriage 92. In this manner, an operation of keeping the image sensor 90 and the carriage 92 in a predetermined engaging state and further connecting the electric cable is difficult, which often causes a problem that a worker comes in contact with the upper surface 91 of the image sensor 90. The upper surface 91 is an optical path for reading an image of a recording-objective medium, and hence there is a problem if scratching, fogging or the like due to the contact by a worker occurs, a read image by the image sensor 90 deteriorates.